Since the explosive growth in wireless communications is a worldwide phenomenon, the next generation of mobile phones, also known as 3G (third generation) or UMTS (Universal Mobile Telecommunication Services), is a technology that allows users to access e-mails, videos and webs via a mobile phone.
Many companies, such as Motorola and Samsung, have provided 3G mobile phones that possess two displays. These kinds of mobile phones offer people two viewing options. A large interior display is used for standard functions and an exterior one just shows a caller's ID or, time and date. According to this, the resolution of the interior display is much higher than the exterior one. The interior display with higher resolution is sometimes an active matrix liquid crystal display (AMLCD). The exterior display with less electrical consumption is a passive matrix LCD (PMLCD).
A liquid crystal (LC) layer of the PMLCD is sandwiched between an upper glass substrate and a lower glass substrate. A first set of electrical lines (electrodes) aligned in a row configuration and a second set of electrical lines aligned in a column configuration are located between the LC layer and the upper glass substrate, and the LC layer and the lower glass substrate, respectively, to form a matrix mode. In the matrix mode, each intersection of the electrical lines aligned in the row configuration and the electrical lines aligned in the column configuration is a pixel. When applying a voltage difference between the row and column electrical lines, alignments of the LC molecules change and the gray scale of the pixel is thus determined.
AMLCD is similar to the PMLCD. The major difference between the AMLCD and the PMLCD is that the AMLCD further comprises a switching device (e.g. thin film transistor; TFT) at its each pixel so as to provide faster switching rate and more image displays.
Referring to FIG. 1, a simple comparison between the AMLCD and PMLCD is shown. The electrical consumption of PMLCD is much less than that of AMLCD. The resolution and contrast ratio of AMLCD are higher those of AMLCD. In addition, the manufacturability of the AMLCD is much more complex than that of the PMLCD.
In order to include all the advantages that AMLCD and PMLCD have within a mobile phone but reduce the weight and the thickness of the mobile phone, it is required to integrate the active and the passive matrix modes within one LCD panel.